This Standard establishes (1) Practice for the construction of spindle noses for horizontal boring machines by showing a number of types of such construction, (2) the important dimensions for self-holding and steep machine tapers as well as drive keys, draw bolts, drift and keeper key slots, bolt circles for face mounting of milling cutters, etc., (3) the corresponding dimensions for the taper shanks for construction of tools (boring bars, arbors, etc.) to fit the spindle nose tapers. The purpose of such construction is to provide an accurately machined socket to locate tools with means to positively hold them in positions in the spindle as well as with means to positively drive the tools.